Fig. 4. (a) Spin–phonon coupling decomposed by vibrational mode into spin–phonon-coupling coefficient between 0 and 500 cm⁻¹ (modes with are omitted for clarity). Values are expressed in units of Å⁻² (b) total SPC (cumulative) of all modes with increasing energy. Large increases in SPC generally occur stepwise, with single highly coupled modes contributing heavily to SPC. Values are expressed in units of Å⁻². In both (a) and (b), the energy range below 300 K (208.5 cm⁻¹) corresponding to modes thermally occupied at room temperature, is highlighted in purple (c) atom-resolved vibrational density-of-states (DOS) for 1–3.